What should I look for in a sleeping bag?
Understand the sleeping bag temperature rating scale
Bags which display a “lower-limit” as well as a “comfort” rating were rated according to the European Norm (EN) standard. The “lower-limit” rating corresponds to the temperature at which the average male would be comfortable and is lower than the “comfort” rating, which corresponds to the temperature at which the average female would be comfortable. Anticipate the coldest temperature you may experience when choosing your sleeping bag (note that it is also possible to increase temperature ratings by wearing layers, etc.).
As such, men should pay attention to the “lower-limit” rating and women (of average hairlessness) should take note of the bag’s “comfort” rating. Personal temperature preferences are not reflected in these ratings, so keep that in mind.
A WORD ON SLEEPING PADS
Your sleeping pad (or lack thereof) also affects your comfort level. Sleeping pads insulate you and your bag from the ground. Because the bottom of your bag will compress when occupied, sleeping pads are very effective insulators in cold-weather environments (think desert or snow).
CONSTRUCTION IS KEY
Sleeping bags insulate by trapping air against your body. The two major types of insulation are natural down and synthetic fibers. Down is a very efficient insulator and is used to create most lightweight sleeping bags. On the other hand, down quickly loses insulating capacity when wet, whereas synthetic fibers are slightly more resilient.
Fill-power is simply a measurement of insulating efficiency (think temperature rating vs. weight). The higher the number, the more insulation the fill provides for the same amount of weight.
BAG TYPES FOR ALL
Sleeping bags designed for backpacking utilize a space-saving “mummy” design and use the lighter-weight materials noted above. Car-camping bags are usually rectangular, often made form cotton or polyester, and make poor backpacking bags on account of their weight.
Never keep a sleeping bag in its stuff sack longer than you have to, especially if it was put away wet. To maintain your bag’s EN rating, you should store your bag in its accompanying storage bag (NOT the compression bag) or a large garbage bag.